list: add list_first_entry_or_null()
This adds the macro list_first_entry_or_null().
Signed-off-by: Alexandre Bailon <abailon@baylibre.com>
diff --git a/include/linux/list.h b/include/linux/list.h
index 5b8d1df..f62afa0 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -349,6 +349,20 @@
list_entry((ptr)->prev, type, member)
/**
+ * list_first_entry_or_null - get the first element from a list
+ * @ptr: the list head to take the element from.
+ * @type: the type of the struct this is embedded in.
+ * @member: the name of the list_head within the struct.
+ *
+ * Note that if the list is empty, it returns NULL.
+ */
+#define list_first_entry_or_null(ptr, type, member) ({ \
+ struct list_head *head__ = (ptr); \
+ struct list_head *pos__ = READ_ONCE(head__->next); \
+ pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
+})
+
+/**
* list_for_each - iterate over a list
* @pos: the &struct list_head to use as a loop cursor.
* @head: the head for your list.
